Welding of similar or identical materials is a relatively simple process and is routinely performed on a variety of materials. However, the stability and integrity of the welded joints between dissimilar materials is frequently problematic, and depending on the particular materials and configurations, welding of dissimilar materials has also proven to be difficult under field conditions.
For example, dissimilar material arc fusion welding can be employed when joining a relatively wide selection of dissimilar materials. However, as complete control of classical arc fusion welds is typically not achieved, strict limitations must be applied to such welds, especially where welded materials are used in an environment that poses high mechanical and/or chemical stress on the weld. Thus, dissimilar material arc fusion welds are often considered to have an increased risk of failure. In other known approaches, friction welding can be employed to fuse dissimilar materials in a process that is conceptually simple and does not require filler metal and flux. Additionally, friction welding advantageously increases stability and integrity in a variety of material combinations as compared to arc fusion welding of dissimilar materials. However, in most cases friction welding requires specialized equipment and is often limited by the particular configuration of the materials to be welded. Therefore, friction welding is generally not recommended for most welding needs in the field.
To overcome problems associated with the above welding processes, mechanical joints for dissimilar materials can be implemented. Examples for such joints are described in U.S. Pat. Nos. 255,163, 831,588, 2,159,811, 3,858,911, and 4,712812. While such joints frequently allow coupling of dissimilar materials under field conditions, numerous difficulties nevertheless remain. Among other things, problems are often encountered with the design, modeling, bolt torquing, and bolt tensioning of these joints, typically leading to leakage or even failure of such joints. Still further, installation of such mechanical joints is often time consuming, especially where the dissimilar materials are pipes with relatively large diameter.
Therefore, while numerous compositions and methods of joining dissimilar materials are known in the art, all or almost all of them suffer from one or more disadvantages. Thus, there is still a need to provide improved composition and methods to reliably weld dissimilar materials to form a stable material connection, especially under field conditions.